The purpose of this proposal is to assess the effect of moderate alcohol consumption at different stages of pregnancy on the risk of spontaneous abortion (SAB), using a unique data base. Heavy alcohol consumption during pregnancy is known to cause adverse reproductive outcomes, but studies on moderate consumption are less consistent. This is an important public health issue because "social" drinking of alcoholic beverages is very common in the United States, so if it represents a risk factor for SAB, many pregnancies are potentially affected. On the order of 10-15% of pregnant women experience a clinical spontaneous abortion and another 20% of conceptuses may be lost before pregnancy is medically recognized. The critical period of exposure to alcohol is unknown. Although many women follow advice to decrease alcohol consumption once pregnancy is recognized, their consumpiion before or very early in pregnancy may be important, warranting further public health intervention. This study will be one of the largest prospective studies of SAB to examine alcohol exposure. Data were collected in a multi-center study of pregnancy outcome recently conducted by the California Department of Health Services and the Kaiser Permanente Medical Care Program. Pregnant women (5300) from three Kaiser facilities were interviewed during their first trimester about a variety of factors, including usual alcohol consumption before pregnancy, whether and when it changed during the first trimester, and maximum consumption. The information on change in usual alcohol consumption provides data on exposure before and during early pregnancy, as well as a more accurate assessment of weekly exposure than is obtained by asking women how much they "usually" drank during pregnancy. Another feature of the data is the information on the greatest amount of alcohol consumed on one occasion and when in pregnancy it occurred, which can be used as a measure of binge drinking. The analysis will use proportional hazards models to calculate the risk of SAB by gestational age, with alcohol consumption during a specified time period as the primary explanatory variable, adjusted for other covariates. The models will be expanded to examine alcohol as a time-dependent variable as well. Mechanisms of action will be further explored by comparing results between sub-sets of SABs which may have different etiologies. Funds are being sought to provide a research analyst, biostatistical consultation and other support to conduct these complex analyses.